This invention relates generally to a phase and frequency lock system and, more particularly, to a system in which a slave signal is phase and frequency locked to a master signal during a predetermined phase interval of the slave signal.
Phase and frequency lock systems are used in many applications to produce phase coincidence between master and slave signals. One common application is coherent radar in which a reference signal is locked to a transmitted signal and then phase-compared to an echo signal. Other applications involve standby and uninterruptible power supplies, television color control circuits, laboratory measurement and instruction instruments, etc. Typically, a slave signal generated by a relatively unstable oscillator is forced into phase with a master signal. Because of variation in the slave signal's frequency, that technique entails substantial phase shifting of the slave signal and results in transient disruptions thereof. Such disruptions, even though momentary, are undesirable for many applications.
The object of this invention, therefore, is to provide an improved system for phase and frequency locking a slave signal to a master signal.